1. Field of the Invention
The present invention relates to an apparatus with an ultraviolet (UV) source for UV heating and photochemical treatment of substrates, including semiconductor substrates, and a method for processing said substrates using said apparatus. It finds particular application in etching, cleaning, or bulk stripping of films or contaminants from the surface of a semiconductor substrate at temperatures of about 400.degree. C. or less for use in the fabrication of integrated circuits.
2. Description of the Related Art
In the processing of semiconductor substrates, including cleaning, etching or other treatments, it is well known to use ultraviolet (UV) activated gases. U.S. Pat. No. 5,580,421 to Hiatt et al, incorporated herein by reference, describes an apparatus for processing a substrate with a UV activatable conditioning gas. In copending application Ser. No. 08/621,538 filed Mar. 25, 1996, incorporated herein by reference, a method of removing undesired material from a substrate using fluorinated gases is disclosed. In copending application Ser. No. 08/818,890 filed Mar. 17, 1997, incorporated herein by reference, a method using UV/halogen for metals removal is disclosed. Because chemical reaction rates are generally temperature dependent, the efficiency of a treatment can be dependent on the temperature at which the treatment is run. It can be desirable to preheat a substrate in a well controlled manner to a preferred process temperature above ambient temperature to provide enhanced process performance. Heating may also be used to thermally desorb volatile species adsorbed on the surface of a substrate.
There are a number of ways of heating a substrate in preparation for chemical processing or for thermally desorbing volatile species. The conventional way of heating, placing the substrate directly on a heating element, does not allow for access to both sides of the substrate. This can pose a problem in particular where one wishes to process both sides of a substrate. This also does not allow for multitemperature sequences with reasonable throughput.
Another way of heating a substrate is by applying a heated gas to the substrate. The use of a heated gas to heat a substrate is inefficient, however.
Yet another way of heating a substrate is via the application of infrared (IR) radiation to the substrate as in rapid thermal processing. However, if both heating and UV illumination are required this introduces considerable engineering difficulties, adding to the expense of any processing tool so equipped. These difficulties include control over stray chamber heating, control over the substrate temperature, and the logistics of incorporating an IR bulb, a UV bulb, and their respective control systems together in an apparatus.
The drawbacks of the above heating methods in the treatment of semiconductor substrates highlight the need for an inexpensive method to uniformly heat substrates to a desired process temperature and provide UV illumination in a single apparatus.